1. Field of the Invention
The present invention relates to a system that uses countercurrents to clean small granule sized substrate, such as Aragonite sand, found within a typical aquarium, as well as to remove dissolved nitrogenous waste material that has accumulated within the aquarium.
2. Background of the Prior Art
Most aquaria include, among other features, a layer of substrate or granular material which covers the bottom of the display tank. It has been observed that besides its aesthetic function, this substrate layer serves as a trap for the purpose of accumulating waste materials produced, either directly or indirectly, by the aquarium inhabitants. At the same time, dissolved nitrogenous waste materials accumulate in the aquarium water, necessitating removal of these materials by periodic water changes. The most efficient means of addressing both of these problems is to remove water from the system for the purpose of changing the water while simultaneously cleaning the substrate with a substrate-cleaning device.
Since the 1950s, several devices have been proposed for the removal of waste material embedded in and adhered to aquarium substrates. By far the most commonly used device in use today is the standard gravel cleaner (used in one form or another for at least the last several decades). The typical gravel cleaner comprises a larger diameter tube or housing attached, in series by means of a reducing coupling, to a smaller diameter siphon hose. In operation, water and gravel are ingested into the bottom of this hand-manipulated device through a large diameter aperture at the base of the housing (large diameter) tube. The gentler flow within the housing allows constant mixing of aquarium water and gravel that has been ingested through this aperture. Loose deposited debris rises immediately through the column of the housing tube and out of the top of the housing via the siphon tube by virtue of its lesser specific gravity. Collisions between gravel particles in the gravel-water slurry within the housing tube result in removal of some of the organic film that covers each gravel particle. The substrate material is too heavy to exit the top of the device housing with the waste (except during transfer of the device from one location to another if the tube has been allowed to fill with too much substrate). Accumulated substrate suspended within the device housing is then returned to the aquarium by tilting the device or by occluding the siphon hose. The device is simple to set up and loss of substrate is soon minimized as the aquarist gains expertise in the use of the equipment.
A far less commonly used device to clean the substrate and to remove dissolved nitrogenous waste material within an aquarium leaves apertures in the housing tube through which water enters forcefully when the relatively large bottom aperture of the housing is blocked by contact with the bottom surface of the aquarium. These apertures, which act as jets, can be directed in such a way as to cause the water-gravel slurry to rotate in vortex fashion within the housing tube to increase the number of substrate particle collisions as well as the force of such collisions. However, these prior art devices suffered from their inability to completely seal the device against the bottom of the housing tube resulting in decreased force of flow through the apertures. Additionally, such prior art devices use an in-line pump/filter arrangement to force water through the device. While having the advantage of reducing the operation to a single step, this approach results in one of two potential disadvantages. The use of finer filter media traps the smaller particles of sediment removed by the device but results in diminished flow through the device because the pump must force water through a filter which quickly plugs up with sedimentary material. The use of coarser filter media results in decreased resistance to flow and thus better removal of adhered organic material by the device, but allows the smaller particles of sediment past the filter and back into the aquarium, hence the loss of efficiency in the form of retained particulate organic carbon (POC) within the aquarium system. This conundrum (loss of efficiency on either side of the filter-medium fineness curve) is an inherent property of in-line pump/filter use.
Nevertheless, the typical gravel cleaner has functioned reasonably well in salt-water systems using crushed coral aggregate as substrate for many years. The comparatively gentle mixing of water and gravel at the base of the device, while enough to remove non-adhered sediment, tended to leave most of the thin film of adhered organic material coating the individual gravel particle which was left within the aquarium system. This material, when further degraded by bacterial action, contributed to the total dissolved organic carbon (DOC) load of the system, thereby increasing nutrient levels in the water. Increased nutrient load is particularly undesirable for aquarists attempting to maintain delicate invertebrates like corals because the nutrients function as fertilizer for the algae which then compete successfully with the corals for space on the rock-pile. Aquarists attempt to balance nutrient import (feeding the system) with nutrient export (waste material successfully removed from the system) in order to maintain the low nutrient level conditions which favor the growth of marine invertebrates and which most closely replicate conditions on the natural coral reef. The functions performed by substrate cleaning are performed by tide and wave action on the coral reef, thus maintaining the low-nutrient conditions in which the organisms inhabiting this delicate ecosystem evolved.
In addition to the above-mentioned limitation of the typical gravel cleaner, the introduction of aragonite sand onto the aquarium industry introduced a new complication. While the sand was aesthetically superior, cleaning this substrate was complicated by the fact that the lighter sand particles would be vacuumed out of the system along with the particulate organic waste if a typical gravel cleaner was used. This problem could be addressed by using a smaller diameter siphon tube with the typical gravel cleaner, slowing the rate at which water rises inside the device and preventing substrate loss. However, this limitation slows even further the turbulence at the base of the device, allowing even more adhered waste to remain behind after the cleaning, resulting in diminished nutrient export. This difficulty has, in part, resulted in the development of a school of thought advocating no substrate cleaning at all. Failure to clean the substrate has proven to be even more deleterious to the aquarium inhabitants because the finer substrate impedes the flow of water below its surface and allows the establishment of zones of anaerobic bacterial degradation. These zones, in turn, allow the buildup of highly toxic sulfur-bearing compounds which may be liberated into the aquarium water whenever the substrate is disturbed by action of fish or by rearrangement of decorative rocks.
Yet another school of thought (called the Berlin method) eliminates the substrate altogether, allowing the aquarist to suction the waste material directly off the bare base of the aquarium. This, to most, is aesthetically unappealing & allows algae to directly colonize the aquarium bottom. In addition, the lack of substrate results in less sediment trapping & increased accumulation of sediment directly on corals & inaccessible areas of the rock pile.
What is needed is a device that addresses the above stated shortcomings in the art by providing a system that greatly improved separation of substrate and waste material in comparison to the prior art gravel cleaners.